The long-term objective of this project is to understand the mechanism of tissue-specific response to steroid hormones. The features of the androgen-dependent cell will be defined by comparing the characteristics of cells that exhibit a pleotropic response to androgens to those of cells that have a more limited response. The specific aims of this project are: (1) to determine if there is a difference in the androgen receptor between androgen-dependent and androgen-sensitive cells, (2) to map for chromosomes associated with androgen-induced cell proliferation, (3) to determine if there are androgen-induced proteins that are involved in the acute phase of the growth response and (4) to determine if androgen-induced cell proliferation is tightly linked to induction of differentiated cell function. A new in vitro model will be used for these studies that consists of cloned hybrid cell lines formed by fusing rat prostate and mouse kidney cell. These hybrids vary markedly in terms of growth rate, morphology, chromosome content, androgen receptor levels and proliferative response to androgens. They are, therefore, particularly useful for studying the properties of hormone-sensitive versus insensitive cells under defined conditions.